This invention relates to vertical shaft impact crushers, and particularly to protective guard rings for such crushers to protect against the abrasive action of rock fragments and rock dust.
The vertical shaft impact crusher has a cylindrical rotor which rotates on a vertical axis within a crusher tank and throws rock, which is fed axially into the rotor, radially outward against a breaker ring where the rock shatters and falls through an opening in the bottom of the tank. Crushers of this variety are relatively inexpensive and reliable and are in wide use because their advantages are well recognized. However, there are some defects in existing vertical shaft impact crushers which have retarded their adoption by the industry, because the inefficiencies which they introduce tend to offset the inherent advantages to this type of crusher.
One of the persistent problems which users of this type crusher have encountered is a high rate of erosive wear of the surfaces which face that breaker ring. This erosive wear is a result of rock fragments rebounding from the breaker ring. Numerous efforts have been made to solve the problem but they have been either unsuccessful or too expensive. One technique is to manufacture wear plates which lie on the floor and the ceiling of the rotor impeller chamber and have a flange which covers the radially facing surfaces of the rotor. This is generally satisfactory from the wear point of view; however, it is expensive and requires replacement of the entire plate when either the flange or the plate becomes worn.
Another problem with prior art vertical shaft impact crushers is intrusion of rock dust or rock fragments into the radially interior region above the rotor and into the bearing cartridge beneath the rotor. Intrusion of rock fragments above the rotor is undesirable because the fragments do not tend to be expelled naturally and simply tumble about causing continuous erosion of the structures at the top of the rotor until they are reduced to dust and are blown out, or until they are manually removed. Intrusion of dust and rock particles into the bearing cartridge can cause damage to the bearing if they actually intrude into the bearing itself. The rock dust is particularly abrasive and can cause rapid damage to a bearing. Most bearings have some sort of dust seal, but the dust seal can be overwhelmed and contaminated with dust if the vicinity of the seal is not maintained relatively clean.
Still another problem with prior art vertical impact crushers is severe abrasion of the interior of the crusher tank. This abrasion is a result of rock fragments rebounding from the breaker ring. Prior attempts to solve this problem involve the use of rigid circular plates placed in front of the tank wall to intercept deflected rocks. This approach fails to dissipate the velocity of deflected rocks and also contributes to the already significant noise level of the vertical shaft impactor.
Accordingly, there has long existed in the industry a need for a vertical shaft impact crusher in which the top and bottom wear plates are separate from the radially facing wear surfaces, and in which provision is made for protection of the radially inner regions of the rotor top and bottom structures and the inner tank wall from intrusion by rock dust and particles to protect against errosive damage thereby.